1. Field of the Invention
The present invention relates to an ultrasonic endoscope having having an ultrasonic probe for generating ultrasonic oscillations and detecting resulting reflected waves.
2. Description of the Related Art
Recently, there have been developed ultrasonic endoscopes in which an ultrasonic transmitter-receiver (ultrasonic probe) is attached to the distal end of an insertion section of the endoscope, in order to facilitate close examination of internal organs in the depths of the human body through the body cavity.
The ultrasonic endoscopes may be roughly classified into two types, mechanical and electronic ultrasonic scanning types. Among the endoscopes of the mechanical scanning type, radial-scanning endoscopes, in which an ultrasonic transmitter-receiver is rotated around the central axis of the insertion section, is adapted for ultrasonic diagnosis through the lumina, such as the alimentary canals.
Typical radial-scanning ultrasonic endoscopes are disclosed in Published Unexamined Japanese Patent Application No. 60-227740 or Published Unexamined Japanese Utility Model Application No. 61-57908, for example. In these ultrasonic endoscopes, an ultrasonic transmitter-receiver attached to the distal end of an insertion section of the endoscope is rotated by means of a motor through the medium of a hollow drive shaft. A signal from the transmitter-receiver is fetched from a rotary signal transmission unit at the proximal end portion of the drive shaft, through a signal cable passed through the hollow portion of the shaft. The motor and the signal transmission unit are housed in an auxiliary operating section, which is disposed between the insertion section and an operating section of the endoscope.
If the auxiliary operating section is interposed in this manner, however, the distance between the respective grip portions of the insertion section and the operating section is too great for an operator to hold the two grip portions at the same time, so that the operating efficiency is lowered.